Excess nitrogen input to water bodies is becoming a substantial environmental concern. In general, elevated concentrations of nitrogenous species (N), such as ammonium or nitrate, spur eutrophication, which can lead to hypoxia, odors, color, and other undesirable water-quality changes. Ammonium also can be directly toxic to fish and exhibits a large oxygen demand. Furthermore, elevated levels of nitrate in drinking water cause methemoglobinemia in infants (Maxcy, 1950; Masters, 1998). As a result, the USEPA set the maximum containment level (MCL) for nitrate to 10 mg NO3−—N/l for drinking water (Masters, 1998). Ironically, the problems of N in water environments demand concentrations far lower than the MCL. In the future, wastewater discharge standards for total N may be as low as 1 to 3 mgN/L when the watershed is sensitive to eutrophication or hypoxia.
Ammonium is the most usual form of nitrogen pollution in wastewaters of various types. It is produced during the production of fertilizers and chemicals. As a result, large amounts of ammonium are present in agricultural runoff and discharges from the fertilizer industry. Ammonium pollution also is attributed to over-fertilization and intensive livestock farming. Another major source of ammonium nitrogen is domestic wastewater, since the N present in organic material in human wastes is ammonium or organic N that can be hydrolyzed to ammonium.